Greases containing amidourea thickeners



United States Patent 3,346,497 GREASES CONTAINING AMIDOUREA THICKENERSJohn L. Dreher, Berkeley, and Bruce W. Hotten, Orinda,

Calif., assignors to Chevron Research Corporation, a

corporation of Delaware No Drawing. Filed Apr. 1, 1965, Ser. No. 444,803

9 Claims. (Cl. 25251.5)

ABSTRACT OF THE DISCLOSURE High temperature greases comprising alubricating oil base and as a thickener therefor, an amide or imidosubstituted polyurea of from 1 to 3 hydrocarbyl urea groups.

This patent application relates to grease compositions and thickeningagents therefor, which compositions are characterized by their extremehigh temperature stability and outstanding penetration characteristics.More particularly, the application relates to greases thickened withnovel carboxylic acid-ureido derivatives which may be characterized asamides and imides of alkyl and aryl ureas.

Recently, the demand has increased for greases capable of providingeifective lubrication at high temperatures. The demand has beenstimulated by development of modern equipment operating at high speeds,etc., and is evidenced by the many industrial and militaryspecifications which provide minimum dropping point requirements of 400+F. In many applications, operating temperatures of over 500 F. areencountered, and a consequent re quirement has resulted for greases ableto operate at these temperatures. Among the factors contributing tothese demands are the increased driving power of automobiles andaircraft, etc., and reduction in size of gears and other parts resultingfrom streamlining and other like design factors. An example of suchstreamlining is the reduction in total diameter of transmission andpower train equipment in modern automobiles for the purpose of reducingclearances necessary for floors, etc. This results in reduction of geardiameters with a consequent increase in speed and temperature.

Among the materials that have been employed to produce high meltingpoint greases are the salts of certain fatty and other carboxylic acids.Examples of such maten'als of this type which are commonly employed arethe lithium salts of various fatty acids. However, these salts, incommon with other materials of this general type, while providinggreases of high melting points, contribute oxidation-promoting metalions to the grease composition. These ions thus eflFect corrosion of theparts which the greases are designed to lubricate. It is, therefore,particularly desirable to provide high temperature stable greases whichare, in addition, ashless, i.e., do not contain metal ions.

Although numerous non-metallic thickening agents have been proposed,these materials have generally failed to provide sufliciently highdropping points and consequent high temperature stabilities to beemployed successfully in the aforementioned applications. Also, most ofthe ashless materials proposed have failed to provide proper stabilitycharacteristics, that is, such characteristics as are defined in testsas penetration, etc.

It is thus highly important to provide greases which have high droppingpoints, provide excellent lubrication for long periods at such hightemperatures, are ashless and may be easily and economically prepared.

It has now been found that excellent high temperature greases resultfrom the combination of an oil of lubricating viscosity and certaincarboxylic acid-ureido compounds. Thus, the thickening agents of thisinvention comprise materials which may be represented by the formula:

X-(R-NHii-NH).Y in which R is a hydrocarbylene radical of 1 to 30 carbonatoms, n is a cardinal number 1 to 3, and X is a radical selected fromthe group consisting of (a) RC NH in which R is selected from the groupconsisting of alkyl radicals of 10 to 30 carbon atoms and aryl radicalsof 6 to 16 carbon atoms, and (b) o (o) ('i R \N (p) 20 in which R is aspreviously defined and R' is hydrocarbylene of l to 30 carbon atoms, and(b) in which bonds 0 and p, R" and R' are as previously defined, and (c)hydrocarbyl radicals of 1 to 30 carbon 40 atoms.

A preferred species of the invention is a grease thickened by adiamidodiurea derived from two molecules of stearic acid, two moleculesof tolylene diisocyanate and one molecule of p-phenylene diamine.

Thus, the additives of this invention may be described as amides andimides of mono-, diand triureas. These materials are formed by reactingin certain proportions suitable carboxylic acids or internal carboxylicanhydrides, diisocyanates and amines or diamines. The followingreactions illustrate the formation of the various amidoureas of thisinvention.

Monoamidomonoureas are prepared by reacting one molecule of adiisocyanate with one molecule each of a carboxylic acid and amonoamine. correspondingly,

monoimidomonoureas are formed by reacting one molecule of a cyclicanhydride, one molecule each of a diamine and a monoisocyanate. Thefollowing equations using a monoamido compound as an example illustratethese reactions:

Carboxylic Diisoeyanate Monoamine Acid 0 n n R1CNHR2NHCNHR 00 1Monoamidomonourea In the preparation of a monoimidourea, the anhydridereacts with One amine group of a diamine, and the other amine groupreacts with the isocyanate, thus no CO is released.

Suitable carboxylic acids from which R is derived include aliphaticcarboxylic acids of from about 11 to 31 carbon atoms and aromaticcarboxylic acids of from 7 to 17 carbon atoms. Examples of suitableacids include aliphatic acids such as lauric, myristic, palmitic,margaric, stearic, arachidic, behenic, lignoceric acid, etc.; andaromatic acids, such as benzoic acid, l-naphthoic acid, 2-naphthoicacid, phenylacetic acid, hydrocinnarnic acid, cinnamic acid, mandelicacid, etc. Suitable anhydrides which may be employed are those derivedfrom dibasic acids which form a cyclic anhydride structure, for example,succinic anhydride, maleic anhydride, phthalic anhydride, etc.Substituted anhydrides, such as alkenyl succinic anhydrides of up to 30carbon atoms are further examples of suitable materials.

Examples of suitable diisocyanates, from which R is derived, include2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 3,3'-bi-tolylenediisocyanate, diphenylmethane- 4,4'-diisocyanate, etc.

Suitable monoisocyanates and monoamines for the production ofmonoamidoand monoimidomonoureas include phenyl isocyanate and tolylisocyanate, and are preferably derived from aliphatic radicals of 2 to30 carbon atoms or aromatic radicals of 6 to 16 carbon atoms.

The diamines are preferably aliphatic diamines of 2 to 30 carbon atomsor aromatic diamines of 6 to 16 carbon atoms. Examples of suitablediamines are ethylene diamine, propylene diamine, butylene diamine,phenylene diamine, tolylene diamine, etc.

In the formation of diamidodiureas, two molecules of the acid, twomolecules of the diisocyanate and one molecule of a diamine are reactedaccording to the following equation:

The acids, anhydrides, diisocyanates, monoamines and diamines are thesame as employed in producing the monourea materials. Since theanhydride will not react directly with the isocyanate, diimidodiureasare produced by reacting two molecules of the anhydride with twomolecules of the diamine and one molecule of the diisocyanate.

The monoamidotriureas are formed by the reaction of one molecule of thecarboxylic acid, two molecules of the diisocyanate, and one moleculeeach of the diamine and monoamine according to the following reaction:

The imidotriureas are likewise formed by reacting one molecule of theanhydride, two molecules of the diamine, and one molecule each of thediisocyanate and the monoamine.

The thickeners may be easily prepared in situ, i.e., in the lubricantbase, or may be prepared separately and then added to the base. Thematerials may be prepared by blending the several reactants together ina reaction vessel and heating them at temperatures ranging from 70 F. toabout 600 F. for a time suflicient to cause formation of the desiredthickener. For example, in the formation of a diamidodiurea, two molesof carboxylic acid, two moles of diisocyanate and one mole of a diaminemay be blended together to form a uniform mixture, then heated attemperatures within the range prescribed. However, since thediisocyanate reacts with amines at a more rapid rate than with acids, ahigher yield of the diamidodiurea may be obtained if the reaction iscarried forth in separate steps. For example, it is preferable to reactthe diisocyanate first with the acid and then add the amine material.correspondingly, in the case of diamidoand imidoureas, it is alsopreferable to conduct the aciddiisocyanate or anhydride-diamine reactionfirst. In either case, the reaction may be carried out simply by mixingthe reactants together as described, or a basic catalyst may be employedto hasten the reaction. Typical bases which may be employed as catalystsare electron-rich nitrogen bases, such as triethylamine and triethylenediamine. The use of a mild catalyst and a somewhat elevated temperaturefor the reaction is preferable to the use of strong catalysts and lowertemperatures. Strong bases, such as sodium hydroxide or an alkoxide,should not be used, as a possibly resulting uncontrolled reaction maylead to an explosion.

The following examples illustrate the preparation of the variouscarboxylic acid-urea type derivatives and greases which contain them.The examples are only illustrative and are not intended to be limitingof the invention.

Example I.-Preparali0n of diimidodiurea grease in single-step reactionthe synthetic oil and having the following properties:

Penetration, initial (P 256 Penetration, after 60 strokes (P 314 ASTMdropping point, F. (DP) 522 Example II.Preparati0n of diamidodiureagrease employing mineral oil 85.2 g. (0.30 mole) of stearic acid wasplaced in a metal beaker and mixed with 300 g. of a paraflinic oil'having a viscosity of 480 SSU at F. The beaker was placed on a hotplatewith a stirring motor attached and the mixture was heated and stirred atF. until it was dissolved. 2.0 g. of triethylamine was added. 52.2 g.(0.30 mole) of 2.4-tolylene diisocyanatewas then added to the mixtureand the material was heated at F. for twenty minutes until evolution ofCO ceased. 17.0 g. (0.15 mole) of m-phenylene diamine was mixed with 200g. of the base oil and heated on a steamplate at 300 for thirty minutes.This solution was then stirred to suspend the liquified m-phenylenediamine and was added to the reaction beaker. There was no reaction at175 F. The mixture was then heated to 295 F. with rapid stirring, and avery heavy gel formed. 235 g. of additional oil was added; stirring wascontinued. The grease was then heated to 400 F for thirty minutes. 7.0 gof phenyl-alpha-naphthylamine oxidation inhibitor was added. Thematerial was then cooled and milled in a 3-roll mill. To 890 g. of thegrease, 50 g. of additional oil was added and hand mixed. The mixturewas then passed once more through the 3-roll mill, giving a greasehaving a P of 240, P of 284, a dropping point (DP) of 552 F. andcontaining 16.2% of the thickener.

Example III.-Preparati0n of monoamidourea and mixture of synthetic andmineral oil 300 g. of an oil blend comprising 50% of a pa-raffinic baseoil having a viscosity of 150 SSU at 100 F. and 50% of dipropyleneglycol dipelargonate and 102.2 g. (0.36 mole) of stearic acid wereplaced in a large flask equipped with heating jacket and stirringdevice. The mixture was stirred and heated to 150 F. for thirty minutes.All the material dissolved. 5.0 g. of triethylamine was added, and themixture was stirred an additional five minutes. 62.6 g. (0.36 mole) ofan 80:20 isomeric mixture of 2,4- and 2,6-t0ly1ene diisocyanate wasadded to the mixture. Foaming began and continued for thirty minutes. Asolution of 38.5 g. (0.36 mole) of p-toluidine and 200 g. of the oilbase which had been heated to 150 F. was added to the mixture. Themixture became cloudy and somewhat thick. The material was then heatedto 240 F., and 5.0 g. of phenyl-alpha-naphthylamine oxidation inhibitorwas added. Heating was continued. A heavy gel formed at about 250 F. Thegrease was then heated to 350 F., held for thirty minutes, cooled andtransferred to beakers and heated in a 350 F. oven for three andone-half hours with occasional hand stirring. The grease was then cooledand milled in a 3-roll mill. 150 g. of the oil base was added to 650 g.of the grease, and the grease was then milled once more through the3-roll mill. The grease, which contained 22.9% thickener, had a droppingpoint (DP) of 453 F., a P of 229 and a P of 250.

Example IV.Preparati0n of monoamidatriurea grease 17.0 g. (0.15 mole) ofm-phenylene diamine and 16.0 g. (0.15 mole) of p-toluidine were mixedwith 200 g. of a blend of 40% of a mineral lubricating oil having aviscosity of 480 SSU at 100, 45% of pentaerythritol tetracaproate and15% of dioctyl azelate. The mixture was placed on a hotplate and stirredto effect solution. 42.6 g. (0.15 mole) of stearic acid and 300 g. ofthe oil base were placed in a metal breaker and heated to 160 F. withstirring. 52.2 g. (0.30 mole) of tolylene diisocyanate was added to themixture and stirred for five minutes. 2.0 g. of triethylamine was addedto the mixture. The mixture was heated to 150 F. and stirred for thirtyminutes until foaming ceased. The first and second solutions were mixedand heated to 300 F. At this temperature, gelation began, and themixture continued to gel to a heavy grease at 350 F. The grease washeated to 400 F. and held for one hour. The grease was cooled and milledtwice through a 3-roll mill. 15 0 g. of additional base oil was blendedwith 590 g. of the grease, yielding a grease containing 15.9% by weightthickener and having a dropping point of 540 F., P of 246 and P of 290.

Greases containing carboxylic-urea derivatives were prepared accordingto the procedures enumerated above,

(A) California parafiinimbase petroleum oil having a viscosity of 480SSU at 100 F.

(B) Mixture of California paratfinic-base petroleum oil having aviscosity of 150 SSU at 100 F. and 50% dipropylene glycol dipelargonate(C) Mixture of 40% (A), 45 pent-aerythritol tetracaproate and 15%diisooctyl azel-ate (D) Pentaerythritol tetracaproate The anhydrides andthe carboxylic acids which were employed are as follows:

( 1) Stearic acid (2) Oleic acid (3) Hydrogenated fish acid (4)IZ-hydroxystearic acid (5) Phthalic anhydride (6) Hexahydrophthalicanhydride The diisocyan ates are as follows:

(7) 2,4-tolylene diisocyanate (8) :20 isomeric mixture of2,4,2,6-tolylene diisocyanate (9) 3,3'-bi-tolylene diisocyanate (10)Diphenylmethane-4,4'-diisocyanate The dimaines employed are as follows:(11) m-Phenylene diamine (12) Ethylene diamine (13) p-Phenylene diamineThe monoamines which were employed are as follows: (14) p-Toluidine (15)Tall oil fatty amines (l6) Rosin amine The materials in the followingtable were prepared by the methods set forth previously and illustratedin the preceding examples. The materials were each inhibited with about0.5% of phenyl-alpha-naphthylamine.

TABLE I Reactants Sample Thick- ASTM No. Tluckener Type ener, Oil D.P.,P P P 0H0 Anhy- Acid Diiso- Di- Mono percent "F.

dride amine amine cyanate Monoamidourea I WMHHHHWHMHHHNJHrr-nmooooooooooooocooqwcoooomoowqcouooqoo l Fluid at Room Temp.

As can be seen from the extensive data embodied in the above table,greases which are prepared from mineral oils, synthetics, and mixturesof mineral and synthetic oils when thickened by the diamido, diimido,monoimido, urea, etc., of this invention display high dropping pointsand excellent unworked (P and worked (P penetrations. Of specialsignificance are the relatively small differences between the worked andunworked penetrations. Additionally, the work breakdown penetration (Pof selected samples showsexcellent resistance to shear for thesegreases. Note that the grease of Example 'I which employed12-hydroxystearic acid as the amide-forming unit was, however, fluid atroom temperature. Also, it may be noted that Example 18 in whichthickener employed was prepared from a mixed abietyl amine had an ASTMdropping point of less than 300 F. and was essentially fluid in thepenetration test. Thus, amines of this type are not suitable for thepreparation of grease thickeners.

In addition to dropping point, penetration, and aging tests, greasesthickened by monoamido-monoureas were subjected to high speed bearingperformance tests. The particular test employed is known as the NavyHigh Speed Bearing Test as described in Federal Test Method 331.1. Inthis test, a ball bearing was operated at 10,000 rpm. continuously forapproximately twenty-two hours at 350 F. The apparatus was then cooledto room temperature during a period of two hours. The procedure ofoperating at 10,000 r.p.m. at the noted temperature of cooling wasrepeated until there was bearing failure. The Bearing Life is the numberof hours to bearing failure.

The thickeners employed in this test are as follows: X designatesmonoamidourea derived from stearic acid, 2,4- tolylene diisocyanate andp-toluidine. Y design-ates monoamidourea derived from stearric acid,diphenylmethane-4,4- diisocyanate and p-toluidine. Each sample contained0.4% phenyl-alpha-naphthylamine and 2.0% dioctyldiphenylamine ascorrosion and oxidation inhibitors. The oils employed in the tests arethe same as referred to in Table I. Table II embodies the results ofthese tests:

As noted in the table, the mineral oil base grease had a bearing life of172 and 130 hours respectively. This performance under 350 F.temperature is remarkable for a mineral oil. One hundred and fifty hoursperformance at 350 F. is equivalent to between 2,000 and 3,000 hours at250. The Bearing Life of the synthetic oil-based grease was also verygood.

Lubricating oils which can be used as base oils for the greases of thisinvention include a wide variety of oils, for example, naphthenic base,paraffin base, and mixedbased mineral lubricating oils; synthetic oils,such as polymers of propylene, butylene, etc.; propylene oxide polymers;dicarboxylic acid esters, such as those which are prepared byesterifying azelaic acid with Z-ethylhexyl alcohol; and silicon esters,such as tetraethyl silicate, hexa(4-methyl-2-pentoxy)-disiloxa11e, etc.Also, mixtures of synthetic and mineral lubricating oils may beemployed.

The thickeners described in this specification are employed in amountssufficient to thicken the oils to the consistency of grease, that is, inamounts ranging from 5 to 50% by weight, or preferably in amounts fromto 30% by weight.

While the character of this invention has been described in detail withnumerous examples, this has been done by way of illustration only andWithout limitation of the invention. It will be applied to those skilledin the art that numerous modifications and variations of theillustrative examples may be made in the practice of the inventionwithin the scope of the appended claims.

We claim:

1. A grease composition comprising an oil of lubricating viscosity and,in an amount sufficient to thicken said oil to the consistency of agrease, a carboxylic-ureido derivative of the formula:

XR-NHCNH A in which R is a hydrocarbylene radical of 1 to 30 carbonatoms, n is a cardinal number 1 to 3, and X is a radical selected fromthe group consisting of R( 3-NH in which R is selected from the groupconsisting of alkyl radicals of 10 to 30 carbon atoms and aryl radicalsf 6 to 16 carbon atoms, and

in which R is as previously defined and R" is hydrocarbylene of 1 to 30carbon atoms, and

in which R" and R and the bonds (0) and (p) are as previously defined,and (c) hydrocarbyl radicals of 2 to 30 carbon atoms.

2. The composition of claim 1 in which R is an arylene radical of 6 to16 carbon atoms, 21 is 2, X is (a) in which R is an alkyl group of 10 to30 carbon atoms and Y is (a) in which R is an alkyl radical of 10 to 30carbon atoms and R is an arylene radical of 6 to 16 carbon atoms.

3. The composition of claim 2 in which R' is alkyl of 12 to 24 carbonatoms.

4. The composition of claim 3 in which R and R are tolylene radicals.

5. The composition of claim 3 in which R and R are 3,3'-bitolylene and Ris the alkyl radical from stearic acid.

6. The composition of claim 1 in which n is 1 and Y is an alkyl radicalof 10 to 30 carbon atoms.

7. The composition of claim 6 in which X is (a) and Y is an alkylradical of 10 to 30 carbon atoms.

8. The composition of claim 1 in which n is 3 and Y is an alkyl radicalof 10 to 30 carbon atoms.

9. The composition of claim 1 in which the oil of lubricating viscosityis a synthetic oil.

(References on following page) 3,346,497 9 10 References Cited FOREIGNPATENTS UNITED STATES PATENTS 610,969 12/1960 Canada. 2,698,300 12/1954Hotten 252-515 2,710,839 6/1955 Swakon et a1. 252-515 DANIEL Emmmer-2,832,739 4/1958 Swakon 25251.5 I. VAUGHN, Assistant Examiner.

1. A GREASE COMPOSITON COMPRISING AN OIL OF LUBRICATING VISCOSITY AND,IN AN AMOUNT SUFFICIENT TO THICKEN SAID OIL TO THE CONSISTENCY OF AGRESE, A CARBOXYLIC-UREIDO DERIVATIVE OF THE FORMULA: